[RV7A Flyer]

Anybody familiar with the bootstrap Excel spreadsheets that are available from AvWeb, and how to use them? Just ran some flight tests to try to narrow down Vx, Vy, Vbg as well as get the coefficient of drag and all the performance data it spits out, but the values are not lining up to reality (e.g., max level cruise speed is coming out *way* too low, etc.).

If anyone has used these spreadsheets, can you let me know and lend a hand in how to properly acquire/enter the data? Some of the fields are a bit murky...

 

[ChiefPilot]

Anybody familiar with the bootstrap Excel spreadsheets that are available from AvWeb, and how to use them? Just ran some flight tests to try to narrow down Vx, Vy, Vbg as well as get the coefficient of drag and all the performance data it spits out, but the values are not lining up to reality (e.g., max level cruise speed is coming out *way* too low, etc.).

If anyone has used these spreadsheets, can you let me know and lend a hand in how to properly acquire/enter the data? Some of the fields are a bit murky...

I found that they were a gross approximation and that, as you've found, they didn't correspond very closely to values obtained the traditional way. I wonder if it works better as an approximation or rule of thumb for aircraft with a narrower speed range than an RV.

 

[gammaxy]

I've briefly looked at that spreadsheet in the past, assuming it was based on John T. Lowry's paper, "The Bootstrap Approach to Predicting Airplane
Flight Performance". Your post caused me to look a little closer and realize that it isn't.

Lowry's method requires you to perform a "full-speed level run" at the same altitude as the rest of the tests. Unless I am misunderstanding something, the Avweb spreadsheet does not.

Here's a link to Lowry's paper which I now feel is the better method:
http://commons.erau.edu/cgi/viewcontent.cgi?article=1167&context=jaaer

 

[gammaxy]

Your post caused me to look a little closer and realize that it isn't.

Sorry, I just checked this some more and realized the paper I mentioned, the spreadsheet, and the Avweb article are all by Lowry. I still don't understand why the spreadsheet doesn't require you to input a maximum level flight velocity from test, but it is clear he uses a different equation for "e" in the spreadsheet than the paper.